1// Types used in iterator implementation -*- C++ -*-
2
3// Copyright (C) 2001-2015 Free Software Foundation, Inc.
4//
5// This file is part of the GNU ISO C++ Library.  This library is free
6// software; you can redistribute it and/or modify it under the
7// terms of the GNU General Public License as published by the
8// Free Software Foundation; either version 3, or (at your option)
9// any later version.
10
11// This library is distributed in the hope that it will be useful,
12// but WITHOUT ANY WARRANTY; without even the implied warranty of
13// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14// GNU General Public License for more details.
15
16// Under Section 7 of GPL version 3, you are granted additional
17// permissions described in the GCC Runtime Library Exception, version
18// 3.1, as published by the Free Software Foundation.
19
20// You should have received a copy of the GNU General Public License and
21// a copy of the GCC Runtime Library Exception along with this program;
22// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
23// <http://www.gnu.org/licenses/>.
24
25/*
26 *
27 * Copyright (c) 1994
28 * Hewlett-Packard Company
29 *
30 * Permission to use, copy, modify, distribute and sell this software
31 * and its documentation for any purpose is hereby granted without fee,
32 * provided that the above copyright notice appear in all copies and
33 * that both that copyright notice and this permission notice appear
34 * in supporting documentation.  Hewlett-Packard Company makes no
35 * representations about the suitability of this software for any
36 * purpose.  It is provided "as is" without express or implied warranty.
37 *
38 *
39 * Copyright (c) 1996-1998
40 * Silicon Graphics Computer Systems, Inc.
41 *
42 * Permission to use, copy, modify, distribute and sell this software
43 * and its documentation for any purpose is hereby granted without fee,
44 * provided that the above copyright notice appear in all copies and
45 * that both that copyright notice and this permission notice appear
46 * in supporting documentation.  Silicon Graphics makes no
47 * representations about the suitability of this software for any
48 * purpose.  It is provided "as is" without express or implied warranty.
49 */
50
51/** @file bits/stl_iterator_base_types.h
52 *  This is an internal header file, included by other library headers.
53 *  Do not attempt to use it directly. @headername{iterator}
54 *
55 *  This file contains all of the general iterator-related utility types,
56 *  such as iterator_traits and struct iterator.
57 */
58
59#ifndef _STL_ITERATOR_BASE_TYPES_H
60#define _STL_ITERATOR_BASE_TYPES_H 1
61
62#pragma GCC system_header
63
64#include <bits/c++config.h>
65
66#if __cplusplus >= 201103L
67# include <type_traits>  // For __void_t, is_convertible
68#endif
69
70namespace std _GLIBCXX_VISIBILITY(default)
71{
72_GLIBCXX_BEGIN_NAMESPACE_VERSION
73
74  /**
75   *  @defgroup iterators Iterators
76   *  Abstractions for uniform iterating through various underlying types.
77  */
78  //@{
79
80  /**
81   *  @defgroup iterator_tags Iterator Tags
82   *  These are empty types, used to distinguish different iterators.  The
83   *  distinction is not made by what they contain, but simply by what they
84   *  are.  Different underlying algorithms can then be used based on the
85   *  different operations supported by different iterator types.
86  */
87  //@{
88  ///  Marking input iterators.
89  struct input_iterator_tag { };
90
91  ///  Marking output iterators.
92  struct output_iterator_tag { };
93
94  /// Forward iterators support a superset of input iterator operations.
95  struct forward_iterator_tag : public input_iterator_tag { };
96
97  /// Bidirectional iterators support a superset of forward iterator
98  /// operations.
99  struct bidirectional_iterator_tag : public forward_iterator_tag { };
100
101  /// Random-access iterators support a superset of bidirectional
102  /// iterator operations.
103  struct random_access_iterator_tag : public bidirectional_iterator_tag { };
104  //@}
105
106  /**
107   *  @brief  Common %iterator class.
108   *
109   *  This class does nothing but define nested typedefs.  %Iterator classes
110   *  can inherit from this class to save some work.  The typedefs are then
111   *  used in specializations and overloading.
112   *
113   *  In particular, there are no default implementations of requirements
114   *  such as @c operator++ and the like.  (How could there be?)
115  */
116  template<typename _Category, typename _Tp, typename _Distance = ptrdiff_t,
117           typename _Pointer = _Tp*, typename _Reference = _Tp&>
118    struct iterator
119    {
120      /// One of the @link iterator_tags tag types@endlink.
121      typedef _Category  iterator_category;
122      /// The type "pointed to" by the iterator.
123      typedef _Tp        value_type;
124      /// Distance between iterators is represented as this type.
125      typedef _Distance  difference_type;
126      /// This type represents a pointer-to-value_type.
127      typedef _Pointer   pointer;
128      /// This type represents a reference-to-value_type.
129      typedef _Reference reference;
130    };
131
132  /**
133   *  @brief  Traits class for iterators.
134   *
135   *  This class does nothing but define nested typedefs.  The general
136   *  version simply @a forwards the nested typedefs from the Iterator
137   *  argument.  Specialized versions for pointers and pointers-to-const
138   *  provide tighter, more correct semantics.
139  */
140#if __cplusplus >= 201103L
141  // _GLIBCXX_RESOLVE_LIB_DEFECTS
142  // 2408. SFINAE-friendly common_type/iterator_traits is missing in C++14
143  template<typename _Iterator, typename = __void_t<>>
144    struct __iterator_traits { };
145
146  template<typename _Iterator>
147    struct __iterator_traits<_Iterator,
148			     __void_t<typename _Iterator::iterator_category,
149				      typename _Iterator::value_type,
150				      typename _Iterator::difference_type,
151				      typename _Iterator::pointer,
152				      typename _Iterator::reference>>
153    {
154      typedef typename _Iterator::iterator_category iterator_category;
155      typedef typename _Iterator::value_type        value_type;
156      typedef typename _Iterator::difference_type   difference_type;
157      typedef typename _Iterator::pointer           pointer;
158      typedef typename _Iterator::reference         reference;
159    };
160
161  template<typename _Iterator>
162    struct iterator_traits
163    : public __iterator_traits<_Iterator> { };
164#else
165  template<typename _Iterator>
166    struct iterator_traits
167    {
168      typedef typename _Iterator::iterator_category iterator_category;
169      typedef typename _Iterator::value_type        value_type;
170      typedef typename _Iterator::difference_type   difference_type;
171      typedef typename _Iterator::pointer           pointer;
172      typedef typename _Iterator::reference         reference;
173    };
174#endif
175
176  /// Partial specialization for pointer types.
177  template<typename _Tp>
178    struct iterator_traits<_Tp*>
179    {
180      typedef random_access_iterator_tag iterator_category;
181      typedef _Tp                         value_type;
182      typedef ptrdiff_t                   difference_type;
183      typedef _Tp*                        pointer;
184      typedef _Tp&                        reference;
185    };
186
187  /// Partial specialization for const pointer types.
188  template<typename _Tp>
189    struct iterator_traits<const _Tp*>
190    {
191      typedef random_access_iterator_tag iterator_category;
192      typedef _Tp                         value_type;
193      typedef ptrdiff_t                   difference_type;
194      typedef const _Tp*                  pointer;
195      typedef const _Tp&                  reference;
196    };
197
198  /**
199   *  This function is not a part of the C++ standard but is syntactic
200   *  sugar for internal library use only.
201  */
202  template<typename _Iter>
203    inline typename iterator_traits<_Iter>::iterator_category
204    __iterator_category(const _Iter&)
205    { return typename iterator_traits<_Iter>::iterator_category(); }
206
207  //@}
208
209  // If _Iterator has a base returns it otherwise _Iterator is returned
210  // untouched
211  template<typename _Iterator, bool _HasBase>
212    struct _Iter_base
213    {
214      typedef _Iterator iterator_type;
215      static iterator_type _S_base(_Iterator __it)
216      { return __it; }
217    };
218
219  template<typename _Iterator>
220    struct _Iter_base<_Iterator, true>
221    {
222      typedef typename _Iterator::iterator_type iterator_type;
223      static iterator_type _S_base(_Iterator __it)
224      { return __it.base(); }
225    };
226
227#if __cplusplus >= 201103L
228  template<typename _InIter>
229    using _RequireInputIter = typename
230      enable_if<is_convertible<typename
231		iterator_traits<_InIter>::iterator_category,
232			       input_iterator_tag>::value>::type;
233#endif
234
235_GLIBCXX_END_NAMESPACE_VERSION
236} // namespace
237
238#endif /* _STL_ITERATOR_BASE_TYPES_H */
239
240